Question

What is minimum amount of air required per m^3 of gaseous fuel for complete combustion?

(a) 1/21 [(H2/2) + (CO/2) + 2CH4 + 3C2H4] m^3/m^3 of fuel

(b) 1/100 [(H2/2) + (CO/2) + 2CH4 + 3C2H4] m^3/m^3 of fuel

(c) 1/21 [(H2/2) + (CO/2) + 3C2H4] m^3/m^3 of fuel

(d) 1/100 [(H2/2) + (CO/2) + 3C2H4] m^3/m^3 of fuel

This question was addressed to me in homework.

I would like to ask this question from Calorific Value of Fuels topic in chapter Steam Power Plant of Energy Engineering

Answer 1

The correct option is (a) 1/21 [(H2/2) + (CO/2) + 2CH4 + 3C2H4] m^3/m^3 of fuel

Easiest explanation: Volumetric analysis of fuels hydrogen, carbon monoxide, methane, ethane, carbon dioxide and nitrogen is done and required minimum amount of oxygen is found for one m^3 of gaseous fuel:

               O2 required/m^3 of fuel = 1/100[(H2/2) + (CO/2) + 2CH4 + 3C2H4] m^3

As atmospheric air contains 21% of O2 by volume, minimum air required t burn one m^3 of gaseous fuel is given by,

    Minimum volume of air required (cm^3/m^3 of fuel):

               = 1/100 [(H2/2) + (CO/2) + 2CH4 + 3C2H4] 100/21

               = 1/21 [(H2/2) + (CO/2) + 2CH4 + 3C2H4] m^3/m^3 of fuel.